The invention concerns a touch-safe power track connection system.
Current methods of illuminating technology extensively exploit varied lighting effects, and users are no longer satisfied with centrally placed ceiling-mounted lighting fixtures or wall-mounted fixtures carried on arms.
This is particularly the case for lighting workshops, laboratories, shop-windows, studios, exhibition stands and similar rooms where special attention is paid to achieve concentrated lighting effects such that at the time an adequate level of illumination is ensured for the rest of the room. It is also often required that the light distribution between individual, highlighted room portions should be differentiated, i.e. illuminated articles/objects should receive light of differing intensity and from differing directions without causing any disturbing effects by concentrated or scattered light.
To this end power track connection systems have been employed.
The use of power track systems for such purposes is in itself known. Thus, a West German company, Leuchten KG, markets such a system under the trade name ERCO. This 3-phase connection power track system consists essentially of an open rectangular-section aluminium rail having an inner lining made of PVC of similarly sectional shape. The R,S,T phase conductors and the neutral conductor, made of copper, are embedded in the PVC. The earth conductor runs along the length of the lower, open end aluminium rail. The space for the cables, the so-called cableage is accommodated at two sides of a connecting or mounting yoke which is to be fixed to the ceiling and which is formed at the upper part of the rail section.
The manufacture of aluminum rails is well known and essentially consists of a continuous extrusion operation. For aesthetic reasons the rails are colored, preferably by electrolytic oxidation. The earth conductor is rolled into the rail during the manufacture of the latter. The phase-cables take the form of strips. In one of the lower legs of the rail section there is a guiding groove into which the tongue of a phase switch of the adaptor fits.
Lighting fixtures can be fitted into the power track by means of a tailor-made adaptor which has a casing made of plastics with a 3-way press button switch. In one of the possible switching positions the adaptor can be fitted into the power track, during which time the earth cable loop provides the necessary protective earthing. In the zero or neutral position the adaptor and the power track are mechanically locked. In the third switching position connection is established between the copper strip conductors and the four contacts of the track. In addition, the adaptor may be fitted with a selector switch which serves for the selection of the circuit required before the adaptor is fitted.
If any of the embedded conductors is to be switched to some other power track this can only be done if the circuit of this latter is not overloaded thereby.
The power track described above has, besides its advantages (quick and easy installation, easy handling, relatively light weight, etc.) a decisive drawback.
For safety reasons, the R, S, T phase cables and neutral cable must have a gap of 8 mm between the opposite profiles of the aluminium track, but any current-conducting object slimmer than 8 mm can be inserted into the gap remaining in this way, along the whole length of the track. This represents a high accident risk, particularly if it is considered that the tracks generally do not run completely in a straight line but are angled at a given position. In case of repairs during usage, installation, etc. such an open conductor system represents a real danger for causing an accident even for skilled electricians.